The integrated circuits are usually formed on a wafer. A single wafer contains plurality of integrated circuit chips, or dies. An integrated circuit chip or dice, is obtained through a dicing process of sawing the wafer.
During the dicing process, small contaminant residues/particles from sawing the wafer, usually silicon residue, adhere to wafer surface, accumulate in bonding pads and trenched locations. They are difficult to remove in subsequent cleaning processes once in contact with wafer and virtually impossible to remove once trapped in deep trenches. In addition, during the dicing process, the bonding pads are exposed for corrosion to occur. Corrosion can damage the bonding pads leading to poor bonding performance, poor reliability, or even failure of the device. The contaminant particles and corrosion can cause problems at later assembly operation such as wirebonding.
One approach to reducing corrosion during dicing, involves the use of high purity deionized water (DIW) as a coolant for the dicing blade. The cutting area and the rotating blade are ordinarily bathed in a significant flow of deionized water. One also would think that the silicon residue would be flushed away by the water coolant that floods the cutting area. Unfortunately, even under significant flooding, the small silicon particles are not completely flushed away. Worse, the water coolant can lead to a build up of static charge, resulting in accumulation of silicon residues/particles on the bonding pads, as well as contributing to corrosion.
As the semiconductor technology rapidly advances, wafer size is increased, while die size is reduced. This prolongs the time spent for dicing, which leads to more challenges.